Fermentative parameters and aerobic stability of orange peel silage with pelleted citrus pulp

ABSTRACT This study evaluated the effects of pelleted citrus pulp (PCP) added to orange peel on fermentative parameters and aerobic stability of orange peel silages. The treatments were based on different levels of PCP: 0 (control), 10% PCP, 20% PCP, and 30% PCP calculated according to the weight of orange peel (w/w), with five experimental silos per treatment stored for 60 days. Chemical composition, fermentative parameters, microbial population, and dry matter (DM) losses were performed in silages after opening the experimental silos. Furthermore, aerobic stability was evaluated for 12 days. Silages with 10 and 20% PCP presented suitable levels of DM, 226 and 302 g kg−1, respectively, and probably adequate water activity that benefited the lactic acid fermentation, but it jeopardized their aerobic stabilities. The inclusion of 10% PCP did not reduce the effluent loss compared with the control silages. Yet, 30% PCP silage showed the lowest effluent loss (93%), in contrast to the low lactic acid content (35 g kg−1) and short aerobic stability (49 h). Control silages remained stable for a longer period (115 h), but showed greater loss of N as NH3, and higher losses of DM through gas (354 g kg−1) and effluents (114 g kg−1). In short, we highlighted 20% PCP silage because of its high lactic acid bacteria (6.3 cfu g−1), high lactic acid:acetic acid ratio (1.41), low nitrogen degradation as NH3, and reduced gas (67%) and effluent (80%) productions. With the highest lactic acid (66.42 g kg−1), these well-preserved silages showed a more intense aerobic degradation, starting after 42h. The inclusion of PCP to orange peel improves the fermentation process probably due to the decrease of water activity, but decreases the aerobic stability of the silage as well.

摘要 本研究评估了添加颗粒柑橘粕（pelleted citrus pulp, PCP）对柑橘皮青贮饲料（orange peel silages）发酵参数与有氧稳定性的影响。试验设置以柑橘皮重量为基准的不同质量占比PCP处理组：0%（对照组）、10%、20%及30% PCP（w/w），每个处理组设置5个试验青贮罐，贮藏60天。开罐后测定青贮饲料的化学组成、发酵参数、微生物种群及干物质（dry matter, DM）损失量，并开展为期12天的有氧稳定性评估。10%与20% PCP处理组的青贮饲料干物质含量分别为226 g kg⁻¹和302 g kg⁻¹，水分活度适宜，可促进乳酸发酵，但会损害其有氧稳定性。10% PCP处理组的渗出液损失与对照组无显著差异。30% PCP处理组的渗出液损失最低（93%），但其乳酸含量仅为35 g kg⁻¹，有氧稳定性仅维持49小时。对照组的有氧稳定时间更长（115小时），但以氨（NH3）形式存在的氮损失更高，干物质气态损失（354 g kg⁻¹）与渗出液损失（114 g kg⁻¹）也更高。简言之，20% PCP处理组的青贮饲料表现最优：其乳酸菌（lactic acid bacteria）数达6.3 cfu g⁻¹，乳酸与乙酸比值为1.41，氨态氮降解程度低，气态损失率为67%、渗出液损失率为80%。该组青贮饲料的乳酸含量最高（66.42 g kg⁻¹），但有氧降解更为剧烈，于42小时后启动。在柑橘皮中添加颗粒柑橘粕可通过降低水分活度改善发酵过程，但同时会降低青贮饲料的有氧稳定性。